1. Field of the Invention
This invention relates generally to photographic elements and, more particularly, to color diffusion transfer photographic materials.
2. Description of the Prior Art
A color diffusion transfer process using dye developers is described in U.S. Pat. No. 2,983,606. In the color photographic system, a color photographic element is, after imagewise exposure, developed by applying a liquid developing composition onto the surface of the photographic emulsion layer, whereby dye developers are oxidized and immobilized in proportion to the amount of developed silver and, on the other hand, unoxidized dye developers diffuse into the image receiving layer of the photographic element to provide transferred dye images. However, in such a color photographic system, frequently the immobilization of the oxidized dye developers is imperfect and the transfer of dye developers occurs to some extent in the areas in which the dye developers must be immobilized. This results in reducing color separation. Moreover, since the developer moieties of the dye developers transferred into the image receiving layer tend to be oxidized by air and the like, if a stabilization treatment is not employed, frequently the transferred dye images deteriorate and stains form. Therefore, it is desired to transfer dye moieties only in the color diffusion transfer system.
U.S. Pat. Nos. 3,931,144, 3,928,312 and 3,932,380 describe color diffusion transfer processes using dye releasing redox compounds, i.e., nondiffusible compounds in which diffusible dye moieties only are released therefrom by development. Also, U.S. Pat. Nos. 3,227,550 and 3,644,498 and British Pat. No. 1,330,524, describe color diffusion transfer processes using dye releasing couplers, i.e., nondiffusible couplers in which diffusible dye moieties only are released therefrom by development. A "dye releasing redox compound" and a "dye releasing coupler" are essentially different from a "dye developer" because the former type compound or coupler releases the dye moiety only and also differ in reaction mechanism. In these patents and patent applications as indicated above, azo dye moieties are employed as the diffusible magenta dye moieties to be released from the dye releasing redox compounds or the dye releasing couplers. However, such azo dyes have the disadvantage that they fade, after being transferred, due to the action of light or heat, in particular, in a wet condition. Furthermore, these monoazo dyes have also the disadvantage that the hues thereof vary with changes of pH.
Therefore, in the two color diffusion transfer systems described above, it is desired to develop new nondiffusible compounds having dye moieties which have improved fastness to light and heat, whose hues do not vary with changes of pH and moreover which have improved mordantability. In addition, these known azo dyes in many cases exhibit the property of undesired "after-diffusion" from a mordanting layer.